Method and system for characterizing movement of an object

ABSTRACT

Motion of an object is characterized based on data indicative of a plurality of pixilated images of the object. An outline of the object may be extracted from the data for each pixilated image of the object. Changes over time in a shape and/or position of the outline may be used to determine a speed associated with the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/894,029 filed Mar. 9, 2007.

BACKGROUND

1. Field of the Invention

The invention relates to methods and systems for characterizing movementof objects.

2. Discussion

Several techniques are known for determining a speed of a moving object:(a) Direct, active measurement, in which an electro-magnetic field, e.g,radio, infra-red, visible-light, or an acoustic field, e.g., ultrasonic,is directed generally at an object to be measured. Reflected energy isthen analyzed to determine the speed of and/or the distance to theobject. Examples of such systems implementing direct, active measurementinclude radar and lidar. (b) Mechanical measurement, in which anarrangement of detectors is placed such that a moving object triggersthe detectors, and the time difference between the trigger events isused to calculate speed. The detectors may be, for example, beams oflight or mechanical switches. (c) Focus analysis, in which anelectronically-sensed image is analyzed for correct focus, that is,correct setting of the image-forming lens between the object and theimage-sensing element. Such analysis, e.g., image contrast enhancement,parallax analysis, yields a distance to an object. Computing the changein focus-distance permits the computation of a component of speed of theobject.

SUMMARY

A method for characterizing movement of an object having at least onefeature includes identifying data indicative of a plurality of pixelsdefining an apparent shape and apparent size of the at least one featurefrom data indicative of a pixilated image of the object, and classifyingthe at least one feature into one of a plurality of predeterminedfeature classes based on the apparent shape of the at least one feature.The method also includes estimating an actual size of the at least onefeature based on the classification, and determining a parameterindicative of the movement of the object based on the estimated actualsize of the at least one feature, the apparent size of the at least onefeature and a change in the apparent size of the at least one feature.

A system for analyzing movement of an object having at least one featureincludes a processing unit. The processing unit is configured to receivea plurality of pixilated images of the object, extract an outline of theat least one feature from each of the plurality of pixilated images ofthe object, and determine an apparent position of the at least onefeature within each of the plurality of pixilated images of the object.The processing unit is also configured to determine an apparent size ofthe at least one feature for each of the plurality of pixilated imagesof the object, estimate an actual size of the at least one feature basedon at least one of the outlines, and determine a parameter indicative ofthe movement of the object based on the estimated actual size of the atleast one feature, the apparent sizes of the at least one feature, andat least one of (i) the outlines of the at least one feature and (ii)the apparent positions of the at least one feature.

A system for analyzing movement of an object includes a processing unit.The processing unit is configured to receive image input indicative of aplurality of pixilated images of the object and size input indicative ofan estimated size of the object. The processing unit is also configuredto determine a speed of the object based on the image and size inputs,and provide output indicative of the determined speed of the object.

While exemplary embodiments in accordance with the invention areillustrated and disclosed, such disclosure should not be construed tolimit the invention. It is anticipated that various modifications andalternative designs may be made without departing from the scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a motion analysis system according to anembodiment of the invention.

FIG. 2 is a block diagram of another motion analysis system according toanother embodiment of the invention.

FIG. 3 is a block diagram of a calculating logic module according to anembodiment of the invention.

FIG. 4 is a block diagram of a display and overlay logic moduleaccording to an embodiment of the invention.

FIG. 5 is an enlarged view of an output device of FIG. 1.

DETAILED DESCRIPTION

Known techniques for determining a speed of a moving object presentseveral issues. For example, direct, active measurement techniques aredetectable. Third parties may detect the presence of an electro-magneticor acoustic field. Mechanical measurement techniques require that thepath of the object be known in advance so that detectors may bepositioned in that path. These detectors may be susceptible toenvironmental interference. Focus analysis techniques are ineffective inlow-light conditions and cannot concurrently calculate speeds formultiple objects: a lens can be optimally focused to only one distance.Additionally, the above techniques must be performed while the object ismoving, not after the fact.

Certain embodiments of the invention characterize the motion of movingobjects. This characterization may be based on a digital or filmrecording of the moving objects, rather than on the moving objectsthemselves. No additional light or other field source is necessary. Assuch, these embodiments may be undetectable in use.

Frames in a sequence of images may be analyzed to isolate objects fromtheir environment. Frame to frame movements of identified objects aretracked to determine, for example, a speed associated with each of theidentified objects. This information may be displayed with images of theobjects. For example, speed information may be overlaid on or displayednext to its associated object. Speed information may also be displayedon a separate device.

Referring now to FIG. 1, a lens 10 projects an image of an environment12 onto an electronic image sensor 14. CMOS or CCD image sensors may beused. Of course, other suitable image sensors, such as image orthicons,may also be used. This image is scanned by an electronic scanningcircuit 16 and stored in an electronic data storage 18, e.g., memory.Commercially available electronic scanning circuits capable of scanningand analog-to-digital conversion may be used. Suitable custom circuits,however, may also be used. The memory may be static random accessmemory, dynamic random access memory or any other suitable type ofdigital memory.

A calculating logic module 20 analyzes the image elements stored in thememory 18 and characterizes the movement of selected image elements. Asdiscussed below, the calculating logic module 20 identifies regions ofpixels which are moving relative to the overall image and analyzes theseregions to classify them as geometric shapes, e.g., circle, square,etc., and/or real-world objects, e.g. face, car, etc.

The calculating logic module 20 may be a microprocessor or digitalsignal processor with suitable algorithms in firmware or software. Adedicated computational logic block, however, may also be used toprovide increased speed if necessary.

As discussed below, information from the calculating logic module 20 isdelivered to a display and overlay logic module 22 where it is combinedwith image data from the memory 18 and displayed on an output device 24.

Similar to the calculating logic module 20, the display and overlaylogic module 22 may be a microprocessor or digital signal processor withsuitable algorithms in firmware. Other implementations andconfigurations are also possible.

Referring now to FIG. 2, an image storage device 128 is accessed by animage re-creation logic module 126 to deliver a sequence of images to anelectronic scanning circuit 116. Such images are scanned by theelectronic scanning circuit 116 and stored in a memory 118. (Numberedelements of FIG. 2 that differ by 100 relative to numbered elements ofFIG. 1 have similar, although not necessarily identical, descriptions tothe numbered elements of FIG. 1.)

As discussed with reference to FIG. 1, a calculating logic module 120analyzes the image elements stored in the memory 118 and characterizesthe movement of selected image elements. Information from thecalculating logic module 120 is delivered to a display and overlay logicmodule 122 where it is combined with image data from the memory 118 anddisplayed on an output device 124.

Referring now to FIG. 3, a memory interface 32 retrieves stored imageinformation from the memory 18. Each image is a “sea of pixels” and doesnot directly contain any information about objects or portions ofobjects within the image captured. An object analyzer 34, therefore,identifies objects (or portions of objects) within the image anddetermines if they are moving.

The object analyzer 34 examines each image and extracts outlines fromthe background, noting the apparent size and position of these outlineswithin each image. These outlines may be of a portion of an object,e.g., a wheel of a vehicle, a nose of a face, a seam of a baseball,etc., or may be of an entire object, e.g., a baseball. The apparent sizeand position of the outlines is represented as a database schemacontaining mathematical coefficients which represent abstractedgeometric properties of the object. In other embodiments, however, anysuitable representation scheme may be used.

The object analyzer 34 of FIG. 3 extracts this information via edgeanalysis techniques. Any suitable technique, such as theobject-identification or motion-estimation algorithms used in H.264 orMPEG-4 image compression, may also be used. An image is analyzed and“edge” pixels are marked. Adjacent pixels are compared to determine ifthere is a substantial difference in color or brightness. If so, such adifference may define an edge. All “edge” pixels are then analyzed todetermine if they are adjacent to other “edge” pixels. Those that arenot are discarded. The remaining “edge” pixels represent lines. Theselines may be straight or curved and may be open or closed. The lines areanalyzed to find their endpoints. If no endpoints are found, or if theendpoints are close together, the line is considered an outline.

Outlines are compared with a database of known outlines corresponding toknown objects stored in a memory using any suitable image recognitiontechnique, e.g., neural network, heuristic, etc. For example, acomparison of an extracted outline with the database of known outlinesmay reveal that the extracted outline is a tire of a bicycle. Thedatabase further includes dimensions associated with each of the knownobjects. An actual size of the object may thus be estimated based on itsclassification relative to the known objects. For example, the extractedoutline identified as a bicycle tire may be assigned an estimated actualdiameter of 30 inches.

An actual distance from a viewing device to the object may be calculatedbased on the apparent size of the outline and the estimated actual sizeof the object. For example, a baseball is known to have a diameter, D,of 2.866 inches. The apparent angular width, A, of the baseball is knownfrom the image. (It is the portion of the full width of the image.) Fromtrigonometry,

${{Tangent}\frac{A}{2}} = {\frac{D}{2}/d}$

where d is the distance to the baseball. As explained below, thisinformation may be used to determine whether the object is moving.

In other embodiments, focus information from, for example, a camera'sauto-focus may be incorporated into the algorithms used by the motionanalyzer 34 to assist in determining the distance to an object whoseexact size is not known. The use of this focus information may improvethe accuracy of speed calculations compared to circumstances where anapproximate size of the object is merely assumed.

An extracted outline may also be classified into one of severalgeometric categories, e.g., square, rectangle, circle, ellipse,trapezoid, etc., using, for example, any suitable curve-fittingtechnique. The data corresponding to pixels of an outline are “fit” toan equation associated with each category. A fit coefficient is thencalculated. The object outline is classified by whichever categoryyields the best fit coefficient and stored in an object list for thatimage in the memory 36. As discussed below, this information may be usedto determine whether the object is moving.

In the embodiment of FIG. 3, the above analysis is performed for eachframe of data. Each new object list is compared to the previous objectlist. Outlines that, from frame to frame, change position, size and/orgeometric classification are considered moving objects. The objectanalyzer 34 stores a list of all such objects in the memory 36.

The output data structure from the object analyzer 34 is typicallyexpressed in units of pixels and may include information indicative ofan outline's location and size. A motion analyzer 38 examines the datastructure(s) stored in the memory 36 to determine movements associatedwith an object.

Analyzing frame to frame changes associated with an object's outlineyields real-world information about movements of the object associatedwith the outline. In the embodiment of FIG. 3, the motion analyzer 38captures such information via data structures. In one example, themotion-estimation algorithm used by the motion analyzer 38 creates adata structure which identifies, in Cartesian coordinates, a currentposition and size of an outline and a future position and size of theoutline. In another example, the motion-estimation algorithm used by themotion analyzer 38 creates a data structure which identifies an initiallocation, size and velocity for the outline. Any suitable datastructure, however, may be used.

Changes in outline size and/or position are indicative of objectmovement. For example, an object outline that is increasing in sizeindicates that the object is moving towards the viewer. Changes ingeometric classification are indicative of rotation. For example, achange in classification from rectangle to square indicates the objectis rotating relative to the viewer. Of course, an object may translateand rotate. Such translation and rotation may be evident from an objectoutline that is changing in size and/or position and changing ingeometric classification.

In the embodiment of FIG. 3, the motion analyzer characterizes themotion associated with objects by analyzing frame to frame differencesof outlines. Changes in apparent size of an outline may be used todetermine movement away from or toward the viewer. For example, if anobject is determined to be 10 feet away in a first frame of the imageand 12 feet away in a second frame of the image, the object has moved 2feet away from the viewer. Dividing this distance by the time betweenthe two frames, as provided by a timer 42, e.g., a crystal-controlleddigital timer typically included in microprocessor systems, will yield acomponent of speed, Speed_(toward/away), associated with the object.

Changes in apparent position of an outline may be used to determinemovement cross-wise to the viewer. For example, if an outline is locatedat position (0, 0) in a first frame of the image and at position (0, 1)in a second frame of the image, the outline has moved 1 unit to theright of the viewer. The estimated actual size of the object andapparent change in position of its associated outline may be used todetermine an actual distance traveled to the right of the viewer. Usingthe baseball example, the image's movement can be computed in terms ofits own size, e.g., the baseball has moved 2.4 diameters across thefield of view. Therefore, it has moved 2.4×2.866 inches. Dividing thisdistance by the time between the two frames, as provided by the timer42, will yield another component of speed, Speed_(cross-wise),associated with the object.

In the embodiment of FIG. 3, the timer 42 determines the time betweenthe two frames by multiplying the known time between two consecutiveframes by the number of frames between the two instances captured. (UStelevision/video is at 29.997 frames per second. The reciprocal of thisvalue is the frame time. EU television/video is at 25 frames per second.Modern film is at 24 frames per second.) In other embodiments, however,other techniques may also be used.

The above components of speed may be resolved into a resultant speed forthe object using, for example, the following relation

Resultant Speed=√{square root over((Speed_(toward/away))²+(Speed_(cross-wise))²)}{square root over((Speed_(toward/away))²+(Speed_(cross-wise))²)}.

Other approaches are also possible. For example, the distancetoward/away from the viewer as well as the distance traveled cross-wiseto the viewer may be resolved into a resultant distance traveled usingcalculations similar to the above. This resultant distance may then bedivided by the time between the two frames to determine the resultantspeed. Of course, other types of movement such as those includingrotation, may require more complex calculations. These calculations,however, may be performed using any suitable technique.

The functions of the calculating logic module 20 may be implemented in avariety of ways. For example, certain embodiments of the calculatinglogic module 20 identify regions of pixels which are moving, andrecognize regions of pixels as real objects, e.g., a face or a car. Theorder in which these tasks are performed may vary depending on theimplementation. In other words, it would be possible to first identifyas many real objects (faces, cars, etc.) in the image as possible, andthen assess their motion, or first asses—moving regions, and thenidentify them. It is, of course, also possible to perform both tasks inparallel.

In some circumstances, a camera may itself be moving. Certainembodiments are able to detect this motion, compute the camera's speed,and use this to correct other speeds. For example, after the motionanalyzer 38 has determined the motion of multiple objects in the image,it performs an analysis of motion common to all (or most) objects. Ifmost objects are moving from right to left, the camera is moving fromleft to right. If most objects are moving away from the image centertoward all four edges, the camera is zooming in, or moving closer.

A memory interface 44 writes a data structure representing the object,e.g., position, speed, etc., into a memory 46 (FIG. 4). The memoryinterface 44 updates this data structure as often as new data requires.In the embodiment of FIG. 3, the memory interface 44 may be viewed as aspecialized database, with a suitable schema designed to be highlyefficient at representing object-recognition data.

Referring now to FIG. 4, a timer 48 drives a scanning logic module 50 toretrieve image information via a memory interface 52 from the memory 18.Timing pulses from the timer 48 drive a digital counter, which is usedas the address to the memory 18 via the interface 52. The scanning logicmodule 50 sends a current scanning location to a control logic module54, which compares it against the list of moving objects stored in thememory 46. (Note that in the embodiment of FIG. 4, the memory 46 isbeing updated regularly by the calculating logic module 20. This updateincludes, for example, a current location and speed of the object.)

The control logic module 54 searches the list of moving objects to seeif any are located at the currently-scanned location. In the embodimentof FIG. 4, the search is based on Content-Addressable Memory, but othersearch methods may also be used. When the control logic module 54detects a match, it notes the speed data stored in the memory 46,generates character forms, e.g., the numeral “55” and the letters “mph,”and instructs an overlay logic module to overlay the speed informationin that area of the image to be displayed. The overlay logic module 56sends the combined information to the output device 24 via an outputdevice driver 58, using any suitable technique appropriate to the typeof output device 24 being used.

In the embodiment of FIG. 4, the basic overlay technique is similar tooverlay functions already in use to insert picture-in-picture or overlayone video image in a small rectangle on another image. In otherembodiments, however, any suitable display technique may be used.

Referring now to FIG. 5, the display device 24 displays static objects,such as the tree and house, without speed information but overlays speedinformation, e.g., “55 mph,” on the moving object, i.e., the car. Thedisplay device 24 also displays the speed of the car in “kph” and thedistance between the viewing device and the car, i.e., “200 meters.” Inother embodiments, however, such speed and other motion information maybe displayed separate from the image of the object being analyzed.

One of ordinary skill will recognize that the techniques describedherein may be implemented in a variety of configurations andcircumstances. For example, a ballistic targeting system for military orsporting activities may estimate an expected location of a moving targetbased on its current location and determined velocity. A baseball gamemay be analyzed and broadcast with information about the trajectory,spin and velocity of the ball as it is thrown by a pitcher. The speed ofon-coming traffic may be assessed in order to indicate when it is safeto turn along a path crossing such on-coming traffic.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed:
 1. A method for characterizing movement of an objecthaving at least one feature, the method comprising: identifying dataindicative of a plurality of pixels defining an apparent shape andapparent size of the at least one feature from data indicative of apixilated image of the object; classifying the at least one feature intoone of a plurality of predetermined feature classes based on theapparent shape of the at least one feature; estimating an actual size ofthe at least one feature based on the classification; and determining aparameter indicative of the movement of the object based on theestimated actual size of the at least one feature, the apparent size ofthe at least one feature and a change in the apparent size of the atleast one feature.
 2. The method of claim 1 wherein the data indicativeof the plurality of pixels further defines an apparent position of theat least one feature and wherein the determined parameter indicative ofthe movement of the object is further based on a change in the apparentposition of the at least one feature.
 3. The method of claim 1 whereinthe determined parameter indicative of the movement of the object isfurther based on a change in the apparent shape of the at least onefeature.
 4. The method of claim 1 further comprising displaying arepresentation of the determined parameter with a pixilated image of theobject.
 5. The method of claim 1 further comprising determining whetherthe object is moving.
 6. The method of claim 1 wherein the determinedparameter comprises a speed of the object.
 7. The method of claim 1wherein determining a parameter indicative of the movement of the objectincludes determining whether the object is rotating.
 8. The method ofclaim 1 wherein the at least one feature comprises an outline of theobject.
 9. The method of claim 1 wherein the at least one featurecomprises an outline of a portion of the object.
 10. The method of claim1 wherein classifying the at least one feature into one of a pluralityof predetermined feature classes based on the apparent shape of the atleast one feature includes comparing the apparent shape of the at leastone feature with a plurality of shapes corresponding to thepredetermined feature classes.
 11. The method of claim 1 wherein theplurality of predetermined feature classes comprises a plurality ofpredetermined geometric shapes.
 12. A computer-readable storage mediumhaving information stored thereon for directing a computer to performthe method of claim
 1. 13. A system for characterizing movement of anobject having a feature, the system comprising: a computing machineconfigured to receive input indicative of a pixilated image of theobject, identify data indicative of a plurality of pixels defining anapparent shape and apparent size of the at least one feature from theinput indicative of the pixilated image of the object, classify the atleast one feature into one of a plurality of predetermined featureclasses based on the apparent shape of the at least one feature,estimate an actual size of the at least one feature based on theclassification, determine a parameter indicative of the movement of theobject based on the estimated actual size of the at least one feature,the apparent size of the at least one feature and a change in theapparent size of the at least one feature, and provide output indicativeof the determined parameter.
 14. The system of claim 13 wherein the dataindicative of the plurality of pixels further defines an apparentposition of the at least one feature and wherein the determinedparameter indicative of the movement of the object is further based on achange in the apparent position of the at least one feature.
 15. Thesystem of claim 13 wherein the determined parameter indicative of themovement of the object is further based on a change in the apparentshape of the at least one feature.
 16. The system of claim 13 whereinthe computing machine is further configured to display a representationof the determined parameter with a pixilated image of the object. 17.The system of claim 13 wherein the computing machine is furtherconfigured to determine whether the object is moving.
 18. The system ofclaim 13 wherein the determined parameter comprises a speed of theobject.
 19. The system of claim 13 wherein determining a parameterindicative of the movement of the object includes determining whetherthe object is rotating.
 20. The system of claim 13 wherein the at leastone feature comprises an outline of the object.
 21. The system of claim13 wherein the at least one feature comprises an outline of a portion ofthe object.
 22. The system of claim 13 wherein classifying the at leastone feature into one of a plurality of predetermined feature classesbased on the apparent shape of the at least one feature includescomparing the apparent shape of the at least one feature with aplurality of shapes corresponding to the predetermined feature classes.23. The system of claim 13 wherein the plurality of predeterminedfeature classes comprises a plurality of predetermined geometric shapes.24. A system for analyzing movement of an object having at least onefeature, the system comprising: a processing unit configured to receivea plurality of pixilated images of the object, extract an outline of theat least one feature from each of the plurality of pixilated images ofthe object, determine an apparent position of the at least one featurewithin each of the plurality of pixilated images of the object,determine an apparent size of the at least one feature for each of theplurality of pixilated images of the object, estimate an actual size ofthe at least one feature based on at least one of the outlines, anddetermine a parameter indicative of the movement of the object based onthe estimated actual size of the at least one feature, the apparentsizes of the at least one feature, and at least one of (i) the outlinesof the at least one feature and (ii) the apparent positions of the atleast one feature.
 25. A system for analyzing movement of an object, thesystem comprising: a processing unit configured to receive image inputindicative of a plurality of pixilated images of the object and sizeinput indicative of an estimated size of the object; determine a speedof the object based on the image and size inputs; and provide outputindicative of the determined speed of the object.